MemberRepository.java

// java/hello/hellospring/repository/MemberRepository.java

package hello.hellospring.repository;

import hello.hellospring.domain.Member;

import java.util.List;
import java.util.Optional;

public interface MemberRepository {
    Member save(Member member);
    // null이면 Optional로 감싸서 반환하는 기능 - Java8에 추가됨
    Optional<Member> findById(Long id);
    Optional<Member> findByName(String name);
    List<Member> findAll();

}